Buffer Settings for Duplication to LTO 5 Tape

If the backup where made with a 64K blok size they will duplicate as 64K blocksize. New backup made with 256K will duplicate as 256K.

Can this be the case ?

By the way: Set NUMBER_DATA_BUFFERS & NUMBER_DATA_BUFFERS_RESTORE to 256 as well.

Are you using tapes that have been used in another system that did not use the 256kb block size? (or this system before you changed the DATA_BUFFER settings)?

When a tape is written using a particular block size that gets written to its tape header and whenever that tape gets used it will use the original block size.

To clear this setting you need to label the tape.

To test if this is the case just select the unassigned tapes that are ready to use for the next duplication - select to label them but uncheck the Verify box - they will then be relabelled using your current 256kb block size and should then use that from then onwards

It does mean labelling all of you tapes before they get re-used (once they are unassigned  - everything on them expired)

Worth a test

The buffer settings on the appliances have not been modified.  The original backup images are using the default buffer settings:

All tapes being used are brand new, never been used before.  However, I will try taking the next scratch tape and manually labelling it with the verify unchecked.

Thanks,
Aly

Thanks for your help.  I configured the tape size using the touch files, which seemed to work.  

The settings currently show as follows:

Also, we are using AIR with a second identical appliance.  Do these settings need to be configured there as well, or will AIR be unaffected?

That looks fine - the one that is just buffers refers to tape (SIZE_DATA_BUFFERS)

AIR will not be an issue in relation to these but it is nice to have both appliances the same.

Great, thanks for your help.  One last question.  To verify that this is getting better performance, do I just watch the "02/04/2014 10:56:36 - Info bptm (pid=23368) waited for full buffer 5460 times, delayed 17187 times" line in the logs to ensure it drops?

The bptm logs are good for this plus one other location that is really useful for duplications...

Just run an All Log Entries report from the Admin Console for a period before you changed them and a period afterwards

You will see entries something like successfully wrote (duplicate) copy 2 at xxxx MB/s

It is about the only place you see duplication throughputs in clear text - you can export it to a text file, import into excel - sort by message and then have a look at the rates you are getting when duplicating to tape

This will let you do a comparision

before:

Fri Jan 31 14:37:37 EST 2014 Info 11875 Backup successfully  wrote backup id client_1390261365, copy 2, fragment 1, 70248368 Kbytes at 33861.979 Kbytes/sec

After:

Wed Feb 05 11:39:27 EST 2014 Info 13458 Backup successfully  wrote backup id client_1390609931, copy 2, fragment 1, 70282749 Kbytes at 62421.065 Kbytes/sec

So looks much better, thanks.  

However, although the FT buffer settings were set as above, this morning, I see that a SAN client backup failed with the following in the logs: